Humidifying systems of this type are preferably used for the artificial respiration of patients. The inhaled air is conditioned to about 34.degree. C. to 37.degree. C. at 80% to 100% relative humidity. Such a humidifying system has become known from DE-GM 93 07 380. In the prior-art breathing air humidifier, the water to be evaporated enters a heated evaporating chamber from a storage tank via a line. The water level in the evaporating chamber is maintained at a constant value by means of a float valve. The float valve, which is a ball valve in this case, is pressed more or less strongly against the outlet opening of the line leading to the storage tank, corresponding to the liquid level present in the evaporating chamber.
The disadvantage of the prior-art breathing air humidifier is that only insufficient control of the liquid level is possible with the ball valve if the evaporating chamber is in an oblique position.